The present invention relates to a process for reclaiming waste paper so that it can be recycled in the form of a pulp.
Reclaimed waste paper constitutes an important source of raw material for the paper industry. This waste paper is disintegrated in the aqueous phase, most often in a pulper, so as to obtain a pulp which is generally used for the production of wrapping paper and packing board or newsprint. In view of the fact that the extent to which reclaimed fibres are used in packaging products in already very great, other outlets have also been invisaged for waste paper such as production of printing/writing paper or tissue paper. In this case, it is important to have a pulp with a sufficient degree of brightness. A satisfactory degree of brightness can be achieved by using additional deinking and/or bleaching treatments. Other treatments (vat retention, removal of heavy and light impurities, deflaking, refining etc.) are often included in the reclaiming cycles.
It has thus been proposed to reclaim waste paper in several stages including a disintegration stage in the presence of soft water and non ionic detergents followed by deinking by washing the pulp obtained (French Pat. No. 1 363 874 filed on the Sept. 28, 1961 in the name of The Hollified Corp.). Although this type of process enables the inks to be well loosened, it does have certain serious disadvantages due to the presence of quite considerable quantities of ink in the washing water. In fact, if it is desired that a sufficient level of brightness be maintained, these can be recycled only in a limited quantity, which leads to the consumption of excessive quantities of water. Moreover, it is necessary to provide for treatments to remove inks in the washing water circuits, which make the process very complicated. The removal of ink-rich residues originating from these treatments is particularly difficult because of the need to protect the environment. Finally, ink deposits form in the washing water systems.